Loss Modeling for Interlocked Magnetic Cores

In mass production, interlocks are an affordable staking solution for magnetic cores of electrical machines. However, the interlock dowels introduce an increase of core losses, not only for the appearance of conductive paths in the interlock regions, but also for a non-negligible worsening of the magnetic material properties (including the hysteresis losses), both inside the interlocks and in the surrounding areas. This study aims at developing a reliable and accurate three-dimensional FEM model that takes into account the contact resistance between interlocks and laminations, as well as layered regions constituted by damaged materials. The paper includes modelling hints and the fine-tuning of the 3D FEM that includes a detailed modeling of the interlock section. Examples of flux and eddy current density distributions are provided, together with the computation of the total iron losses for a variable number of rectangular dowels in the yoke of stator core samples. The numerical results are validated by experimental measurements conducted on multiple samples having different number of interlocks.